Bacteria cell surface components

Bacteria causing gastrointestinal infection need to penetrate the mucus layer before attaching themselves to the epithelial surface. This attachment is usually mediated by bacterial fimbriae or pilus structures, although other cell surface components may also take part in the process. Adherent bacteria colonize intestinal epithelium by multiplication and initiation of a series of biochemical reactions inside the target cell through signal transduction mechanisms (with or without the help of toxins) (51). 

The capacity of pathogenic bacteria to adhere to mucosal membranes has been exploited in the modification of new mucoadhesive polymers. The ability of bacteria to adhere to a specific target is rooted from particular cell-surface components or appendages, known as fimbriae, which promote adhesion to other cells or inanimate surfaces. Fimbriae are extracellular, long thread-like protein polymers of bacteria that play a major role in many diseases. It has been reported that Escherichia coli adheres specifically to the lymphoid follicle epithelium of the ileal Peyer s patch in rabbits. Similarly, different staphylococci possess the ability to adhere specifically to the surface of mucus gel layers and not mucus-free surfaces. Thus, polymers have been modified by the attachment of these fimbriae to enhance mucoadhesion. An attachment protein derived from E. coli, K99-fimbriae, has been covalently attached to polyacrylic acid networks in an attempt to provide a novel polymer with enhanced adhesive properties (Figure 52.7). ... 

Reviews have appeared on the involvement of plant lectins in the recognition of, and defence against, bacteria and on the structures of plant lectins and the uses of plant lectins in studies of cell-surface components. ... 

Bacteria and their composites with soil minerals or organic matter are capable of taking up a wide range and variety of toxic metals in soil environments. Research done over the last decade or so has greatly improved our understanding of the mechanisms on biosorption of metals and bacte-ria-metal-soil component interactions. However, more studies from molecular level are needed in order to enhance the ability of bacteria and their association with soil components to remediate toxic metals-contaminated soils. The focus of future investigations should be on the mechanisms by which metals are sorbed and bound by bacterial cell surfaces and bacteria-soil/mineral composites. In this connection, X-ray absorption spectroscopy (XAS) is a promising technique because it can provide information about... 

In Gram-negative bacteria which are characterised by a rather complex cell envelope, the CM is also referred to as inner membrane to distinguish it from a second lipid bilayer, termed outer membrane (OM). The space between these two layers is called the periplasm (PP). In the periplasmic space, many proteins are found with a variety of functions. Some are involved in biosynthesis and/or export of cell wall components and surface structures (e.g. pili, flagellae,... 

Lectin pathway, stimulated by binding to a lectin. Lectins belong to a family of proteins called collectins, which are present in blood and bind to bacteria. One lectin, known as the mannose binding lectin (MBL), binds to a sequence of mannose sugars that are part of the carbohydrate on the cell surface of some bacteria. It is the lectin-bacteria complex that activates one of the complement proteins. The components of the pathway are prefixed with a C and a number. 

Neither the mechanisms of the host defence for eradication of challenging Salmonella bacteria, nor the relative importance of the host defence against the various Individual surface components of the bacterial cell envelope are well understood. Since, as was stated above, the O-antlgenic polysaccharide chains apparently play an important role in eliciting an effective host defence of either humoral or cellular nature, we have used the various saccharides described earlier for studies of this problem. 

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